1. Field of the Invention
The present invention relates to a hyper-media system which enables one hyper-media document to be used by a plurality of application processing units in different modes, as well as allowing flexible navigation processing for a hyper-media document.
2. Description of the Related Art
Hyper-media systems deal with various kinds of data such as image data including motion picture and still picture, text data, and voice data. Such systems are implemented with hyper-media architecture provided with a function of executing navigation processing for tracing links between nodes with respect to a hyper-media document. FIG. 8 shows structure of a conventional hyper-media system. As illustrated in FIG. 8, the conventional hyper-media system includes a common processing unit 110 for conducting management and processing of common attributes in a hyper-media document, an application processing unit 120 for conducting inherent processing with respect to a hyper-media document and a storage device 130 for storing a hyper-media document.
The common processing unit 110 includes a node management unit 111, a link management unit 112 and a navigation management unit 113. The node management unit 111 has a function of registering, searching for and deleting various kinds of data including image, text and voice as nodes in the hyper-media architecture. The link management unit 112 has a function of creating a link between two nodes by using a node identifier obtained through the node management unit 111 and registering, searching for and deleting the link. The navigation management executing unit 113 manages a node identifier of a node being referred to by a user and has a function of controlling the node management unit 111 to read appropriate nodes and controlling the link management unit 112 to read a link to be traced in response to an instruction given by a user. The navigation management executing unit 113 has a further function of obtaining node data from the node management unit 111 based on a node identifier of the node to which the link is traced and presenting the obtained node data to a user.
A plurality of the application processing units 120 exists in the hyper-media system, each being formed by an API (Application Programming Interface) for calling the function of the common processing unit 110. Each application processing unit defines the type of data to be stored as a node or a link and stores a hyper-media document in the storage device 130 through the node management unit 111 and the link management unit 112 of the common processing unit 110. With the selection of a node by a user with respect to a read hyper-media document, the application processing unit notifies the navigation management executing unit 113 in the common processing unit 110 of the selection of the node to obtain and output node data of a node to which the link is to be traced.
Navigation processing by the navigation management executing unit 113 such as tracking of a link between nodes is mainly conducted by reading a hyper-media document in which a link whose semantic attribute is set in advance is described and executing a procedure correlated to the semantic attribute of the link.
FIG. 9 is a flow chart showing a conventional navigation processing of this kind. With reference to the figure, upon designation of a part defined as a node in the hyper-media document by the operation such as mouse click (Steps 901, 902), a link identifier correlated with the designated part is obtained by the link management unit 112 (Step 903). Then, a node identifier of a node to be linked with the link specified by the link identifier is obtained by the node management unit 111 (Steps 904, 905). Conducted thereafter are processing for referring to other part of the hyper-media document, that is, individual processing according to a type of data, updating of a node identifier being referred to (node identifier of a current node), and output of node data of a new current node (Steps 906-908).
Thus, the conventional hyper-media system executes navigation processing correlated with a predetermined semantic attribute (inherent semantic attribute) of a link.
Hyper-media document navigation processing by the above-described conventional hyper-media system, however, has a drawback that the processing lacks facility because semantic attributes correlated with a link are so fixed that one hyper-media document can not be used by a plurality of application processing units in different modes.
In addition, since application processing units constituting a conventional hyper-media system is each provided with no function of controlling navigation processing (function implemented by node management means, link management means and navigation management executing means) and counterpart functions of the common processing units are limited, it is impossible to conduct navigation processing coping with flexible processing such as processing inherent to each application processing unit and use of contents of one application processing unit by other application processing unit.